In some applications, it may be desirable to deposit a metallic film only on certain areas of a substrate. Typically, such discriminating results are achieved by depositing a continuous metallic film and subsequently patterning the metallic film using lithography and etch steps. Such lithography and etch processes may be time consuming and expensive, and do not offer the precision required for many applications. A possible solution is the use of selective deposition processes, whereby a metallic film is deposited only in the desired areas thereby eliminating the need for subsequent patterning steps. Selective deposition processes for semiconductor device structures may take a number of forms, including, but not limited to, selective dielectric deposition on dielectric surfaces (DoD), selective dielectric deposition on metallic surfaces (DoM), selective metal deposition on dielectric surfaces (MoD) and selective metal deposition on metallic surfaces (MoM).
Selective metal deposition on dielectric surfaces (MoD) is of interest for providing methods for selectively depositing metal films over dielectric surfaces without the need for complex patterning and etch steps. A common method for producing a substrate including selective metal over dielectric surfaces may comprise a blanket deposition of a metallic film over the entire surface of the substrate, covering both the metal surfaces and the dielectric surfaces, and subsequent forming a photolithography mask layer (or if required a double patterned mask layer) over the surface of the blanket metal film, the mask layer being disposed over the regions where the metallic film is to remain. The substrate is then exposed to a metallic etch process, such as a wet etch or a dry etch, which will remove the metallic film from the exposed regions of the substrate not covered by the photolithographic mask. Subsequent processes may remove the remaining photolithographic mask, thereby forming a substrate comprising a metallic film disposed over a dielectric surface. However, such processes for the formation of metallic films over dielectric surfaces, i.e., blanket deposition, masking and etching, are complex, time consuming, cost prohibitive and such processes only become more complex as device feature size decreases at advanced technology nodes. Accordingly, methods are desired for selectively depositing a metallic film on a dielectric surface relative to a metallic surface and particularly methods for selectively depositing tungsten films on dielectric surfaces.